Language is a rule-governed system made up of components or subsystems that work together in consistent and predictable ways to produce meaning. These subsystems contain language universals that are common to all languages and contrasting features that are specific to each language. (Koda & Zehler, 2008)
Contrasts between languages occur in all the language subsystems and parts of speech may exhibit contrasts in several different subsystems simultaneously. Teachers can use this information when planning and teaching the transfer lesson as they focus instruction on language universals and language-specific features within the different subsystems.
Teachers in biliteracy contexts utilize knowledge of the subsystems and components of language in teaching for cross-linguistic transfer. The subsystems are an organizational framework from which to plan transfer lessons centered in the similarities or differences between two languages.